Facts About Measles

Yes, it is possible that measles could become endemic (constant presence of a disease in an area) in the United States again, especially if vaccine coverage levels in the United States decline.  This can happen when people forget to get vaccinated on time, don’t know that they need a vaccine dose (this is most common among adults), or refuse vaccines for religious, philosophical or personal reasons.

Research shows that people who refuse vaccines often group together in communities. When measles gets into communities with pockets of unvaccinated people, controlling its spread is very challenging while also increasing the likelihood of the virus re-establishing itself in the U.S. Read a CDC description of a recent example of this epidemiologic phenomenon..

High sustained measles vaccine coverage and rapid public health response are critical for preventing and controlling measles cases and outbreaks.

Yes. Since measles is still common in many other countries, this disease will continue to be brought into the United States. Measles is highly contagious, so anyone who is not protected against measles is at risk of getting the disease. People who are unvaccinated for any reason, including those who refuse vaccination, risk getting infected with measles and spreading it to others, including those who cannot get vaccinated because they are too young or have specific health conditions.

If you’re unsure whether you’re immune to measles, you should first try to find your vaccination records or documentation of measles immunity. If you do not have written documentation of measles immunity, you should get vaccinated with measles-mumps-rubella (MMR) vaccine. Another option is to have a doctor test your blood to determine whether you’re immune, but this option is likely to cost more, won’t necessarily be covered by your health insurance, and may take two doctor’s visits. There is no harm in getting another dose of MMR vaccine if you may already be immune to measles (or mumps or rubella).

No. People who received two doses of measles vaccine as children according to the U.S. vaccination schedule are considered protected for life and do not ever need a booster dose.

If you’re not sure whether you were vaccinated, talk with your doctor. More information is available from the CDC about who needs measles vaccine.

Very few people—about 3 out of 100—who get two doses of measles vaccine will still get measles if exposed to the virus. Experts aren’t sure why; it could be that their immune systems didn’t respond as well as they should have to the vaccine. But the good news is, fully vaccinated people who get measles are much more likely to have a milder illness, and they are also less likely to spread the disease to other people, including people who can’t get vaccinated because they are too young or have weakened immune systems.

The measles vaccine is very effective. One dose of measles vaccine is about 93% effective at preventing measles if exposed to the virus and two doses are about 97% effective.

In 2008, 2011, 2013 and 2014, there were more reported measles cases compared with previous years. CDC experts attribute this to:

• More measles cases than usual in some countries to which Americans often travel (such as England, France, Germany, India, the Philippines and Vietnam), and therefore more measles cases coming into the US, and/or
• More spreading of measles in U.S. communities with pockets of unvaccinated people.

For details about the increase in cases by year, see the CDC’s Measles Outbreakspage.

Measles can be brought into the United States from any country where the disease remains endemic or where outbreaks are occurring including Europe, Africa, Asia, and the Pacific Islands. In recent years, many measles cases have been brought into the United States from common U.S. travel destinations, such as England, France, Germany, India, and, during 2014, from the Philippines and Vietnam.

Before the measles vaccination program started in 1963, the CDC estimates that about 3 to 4 million people got measles each year in the United States. Of those people, 400 to 500 died, 48,000 were hospitalized, and 4,000 developed encephalitis (brain swelling) from measles.

 Every year, measles is brought into the U.S. by unvaccinated travelers (Americans or foreign visitors) who get measles while they are in other countries. They can spread measles to other people who are not protected against measles, which sometimes leads to outbreaks. This can occur in communities with unvaccinated people.

Most people in the United States are protected against measles through vaccination, so measles cases in the U.S. are far fewer than the number of cases before a vaccine was available.

Since 2000, when measles was declared eliminated from the U.S., the annual number of people reported to have measles ranged from a low of 37 people in 2004 to a high of 644 people in 2014.

Measles eliminationis defined as the absence of continuous disease transmission for 12 months or more in a specific geographic area. Although there are current outbreaks, measles is no longer endemic (constantly present) in the United States.

In 2000, the U.S. declared that measles was eliminated from this country. The U.S. was able to eliminate measles because it has a highly effective measles vaccine, a strong vaccination program that achieves high vaccine coverage in children and a strong public health system for detecting and responding to measles cases and outbreaks.